Iridium catalyst for metathesis of acyclic olefins

ABSTRACT

Iridium catalyst compositions for the metathesis of functionalized and unfunctionalized acyclic olefins.

This is a division of application Ser. No. 08/088,712, filed Jul. 8,1993, now U.S. Pat. No. 5,352,812.

FIELD OF THE INVENTION

This invention relates to iridium catalyst compositions effective forthe metathesis, with and without significant isomerization, ofunfunctionalized and functionalized acyclic olefins.

BACKGROUND OF THE INVENTION

Catalysts which can isomerize and metathesize olefins are of greatcommercial importance, since, among other utilities, this reaction makespossible the production of olefins in desirable molecular weight rangesfrom olefins in undesirable molecular weight ranges.

Unfunctionalized olefin isomerization/metathesis is practicedcommercially and is traditionally carried out in two steps (G. W.Parshall and S. D. Ittel Homogeneous Catalysis, Second Ed., Wiley, NewYork, 1992, Chapter 4.3). The present invention carries out the samechemistry in one step. Catalysts which can isomerize/metathesizefunctionalized olefins are also of potential commercial importance,since they make possible the synthesis of chemical feedstocks fromhighly functionalized biomass.

Much is known about ring opening metathesis polymerization of cyclicolefins catalyzed by iridium complexes. These are summarized in the bookK. J. Ivin Olefin Metathesis, Academic Press, London, 1983, Chapter2.6.3. However, there are very few references in the literature toacyclic olefin metathesis catalyzed by iridium. Porri et al., DieMakromolekulare Chemie 1974, 175, 3097, and Porri et al., DieMakromolekulare Chemie 1975, 176, 3121, describe a catalyst system[Ir(COE)₂ Cl]₂ +AgO₂ CCF₃ +CF₃ CO₂ H effective for the ring-openingmetathesis polymerization of cyclopentene, cycloheptene, andcyclooctene, and isomerization/metathesis of 1-pentene. However, unlikeApplicants' system, the Porri catalyst system: (1) requires the presenceof CF₃ CO₂ H; (2) discloses a AgO₂ CCF₃ to [Ir(COE)₂ Cl]₂ ratio of 2 to1; and (3) is formed in a two-step process. Additionally, in contrast toApplicants' disclosure, Porri's system is not disclosed for themetathesis of functionalized olefins. Further, in one embodiment of thepresent metathesis method, Applicants have observed that the extent ofisomerization accompanying the metathesis reaction is greatly reduceddue to pre-incubation of the catalyst components prior to addition ofthe starting olefin compound.

Much is known about metathesis of acyclic functionalized olefins usingcatalysts based on molybdenum, tungsten, rhenium, and in some instancesruthenium. These are summarized in J. C. Mol J. Mol. Catal. 1991, 65,145 and K. J. Ivin Olefin Metathesis, Academic Press, London, 1983,Chapter 8. The disclosure of methyl oleate metathesis in the presentinvention is the first example of acyclic functionalized olefinmetathesis catalyzed by an iridium based catalyst.

Other references which discuss related systems are Rossi et al.,Tetrahedron Lett. 1974, 11, 879 and Bianchi et al., J. Organomet. Chem.1980, 202, 99. Rhodium catalysts which can simultaneously isomerize andmetathesize acyclic olefins are disclosed in Hughes et al., U.S. Pat.No. 3,721,718.

SUMMARY OF THE INVENTION

This invention provides a method for the metathesis of acyclic olefincompounds, comprising reacting a starting acyclic olefin compoundcontaining n carbon atoms, in the presence of a catalyst compositioncomprising compounds of Formulas II and III ##STR1## wherein the molarratio of compound III to compound II is at least 3 to 1; and

wherein X is C1, Br, or I; R is a C₁ to C₁₀ fluorinated hydrocarbyl; COEis cyclooctene; L is cyclooctene or P(C₆ F₅)₃ ;and n is an integerbetween 3 and about 60; to yield a mixture of acyclic olefin productscontaining 2 to 3 n carbons.

Preferred embodiments of the method include wherein the components ofthe catalyst composition are pre-incubated prior to addition of thestarting olefin; and wherein the molar ratio of compound III to compoundII is at least 4 to 1.

This invention further provides a catalyst composition comprisingcompounds of Formulas II and III ##STR2## wherein the molar ratio ofcompound III to compound II is at least 3 to 1; and

wherein X is Cl, Br, or I; R is a C₁ to C₁₀ fluorinated hydrocarbyl; COEis cyclooctene; and L is cyclooctene or P (C₆ F₅)₃.

Preferred embodiments of the composition include wherein X is Cl, R isCF₃ ; and wherein the molar ratio of compound III to compound II is atleast 4 to 1.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 demonstrates the metathesis/isomerization reaction products ofthe present invention on 1-hexadecene to yield olefin mixtures of C₈ toC₂₈.

DETAILED DESCRIPTION

Iridium catalysts have been discovered which catalyze isomerization andmetathesis of acyclic olefins. Thus, given an acyclic olefin containing"n" carbon atoms, a range of acyclic olefins containing anywhere from 2to approximately 3 n carbon atoms are produced. The exact range obtaineddepends on the molecular weight of the starting olefin.

Significantly, these catalysts tolerate functional groups in the olefin;e.g., methyl oleate can be broken down into an extremely complex mixtureof acyclic aliphatic olefins and acyclic unsaturated mono- and diestersby these catalysts.

Further, Applicants have found that when compounds of Formula II and 3or more equivalents of compounds of Formula III are allowed to stir incontact with each other for several hours at room temperature prior toaddition of the starting olefin, isomerization is suppressed andprimarily metathesis products are observed. This is demonstrated asshown below using, for example, methyl oleate as the starting olefin.##STR3##

The catalyst of the present invention is prepared in situ by theaddition of the silver salt of a fluorinated acid, AgO₂ CR, to aniridium cyclooctene halide complex such as [Ir(COE)₂ Cl]₂, the structureof which is shown below. ##STR4## When two equivalents of AgO₂ CR areadded to [Ir(COE)₂ Cl]₂, the major products are silver chloride and[Ir(COE)₂ O₂ CR]₂. If two equivalents of AgO₂ CR are added to [Ir(COE)₂Cl]₂ in the presence of a linear olefin, the olefin undergoes doublebond isomerization, but no metathesis of the resulting olefin mixture isobserved. When more than two equivalents of AgO₂ CR are added to[Ir(COE)₂ Cl]₂, the initial products are again silver chloride and[Ir(COE)₂ O₂ CR]₂, but the latter undergoes further reaction with theexcess AgO₂ CR present to give silver metal and higher oxidation stateiridium complexes active for olefin metathesis. Thus, when more than twoequivalents of AgO₂ CR are added to [Ir(COE)₂ Cl]₂ in the presence of anacyclic olefin containing n carbon atoms, the olefin undergoes doublebond isomerization and the resulting mixture of olefins undergoesmetathesis, resulting in a complex mixture of olefins containing between2 and approximately 3 n carbon atoms. The significant dual role of thesilver salt in this chemistry (to precipitate silver chloride in thereaction with [Ir(COE)₂ Cl]₂ and oxidize the resulting Ir(I)trifluoroaceate complex) does not appear to have been recognized byPorri et. al. (see, for example, F. Bianchi, M. C. Gallazzi, L. Porri,and P. Diversi J. Organomet. Chem. 1980, 202, 99).

Recognition of the dual role of the silver salt in this chemistry hasmade possible the following discovery: when a mixture of [Ir(COE)LCl]₂and 4 or more equivalents of AgO₂ CCF₃ is allowed to stir for severalhours at room temperature prior to addition of the acyclic olefin,isomerization is suppressed and primarily the metathesis products of thestarting acyclic olefin are formed.

In principle, any iridium halide complex of the formula [Ir(COE)LX]₂which will react with 2 equivalents AgO₂ CR to give AgX and [Ir(COE)LO₂CR]₂ as products, is a viable catalyst precursor. "X" can be Cl, Br, orI. R can be any fluorinated hydrocarbyl containing between 1 and about10 carbon atoms; e.g., trifluoromethyl, pentafluoroethyl, orheptafluoropropyl. Preferred is CF₃.

The acyclic olefin undergoing isomerization/metathesis can containanywhere from 3 to about 60 carbon atoms. The olefin can befunctionalized; possible functional groups include esters, ethers,halogens, and sulfides.

The reaction can be carried out at temperatures between about 25° and150° C., and pressures between 1 and 100 atmospheres (1 atm=1.01×10⁵Pascals). Temperatures between 25° and 100° C., and pressures between 1and 10 atmospheres are preferred.

The reaction may be carried out in an organic solvent. Suitable solventsinclude benzene, toluene, methylene chloride, acetone, diethyl ether,and tetrahydrofuran. Preferred is an aromatic solvent such as benzene ortoluene.

The catalyst system is somewhat air sensitive and the reactions are bestcarried out under an inert atmosphere, e.g. nitrogen or argon.

[Ir(COE)₂ Cl]₂ is a known compound and can be readily synthesized by oneskilled in this art, and for example, a procedure can be found in thefollowing: J. L. Herde, J. C. Lam3Dert, and C. V. Senoff InorganicSyntheses 1974, 15, 18. [(COE)₂ IrCl]₂ is also available commerciallyfrom Aldrich Chemical Co., Milwaukee, Wis., USA. The salts silvertrifluoroacetate, silver pentafluoropropionate, and silverheptafluorobutyrate are also commercially available; for example, fromthe Aldrich Chemical Company.

The complex {Ir(COE)P(C₆ F₅)₃ Cl}₂ was prepared as follows. [Ir(COE)₂Cl]₂ (1.00 g, 1.12 mmol) and P(C₆ F₅)₃ (1.19 g, 2.23 mmol) (AldrichChemical) were suspended in 30 mL of toluene under a nitrogenatmosphere. The reaction mixture was stirred overnight at roomtemperature, during which time the reactants dissolved to give a clearorange-red solution. Volatiles were removed in vacuo to afford anorange-red foam. The crude product was recrystallized fromtoluene/petroleum ether at -40° C. to afford {Ir(COE)P(C₆ F₅)₃ Cl}₂ as ayellow-orange powder (1.72 g, 89%).

EXAMPLE 1

This example demonstrates the metathesis/isomerization reaction of1-hexadecene to give olefins containing between 4 and 28 carbon atoms,followed by hydrogenation of the product mixture to give alkanes asproducts.

Under nitrogen, silver trifluoroacetate (99 mg, 0.45 mmol) and1-hexadecene (488 mg, 2.18 mmol) were dissolved in 4.0 mL of toluene. Tothis solution was added [Ir(COE)₂ Cl]₂ (78 mg, 0. 087 mmol). Theresulting heterogeneous, orange-red reaction mixture was stirred at roomtemperature for ₂₄ h, during which time it became red-brown. An aliquotwas withdrawn after 24 h, and analyzed by gas chromatography (GC):olefins containing between 4 and 28 carbon atoms each could be detected;hexadecene isomers accounted for approximately 10% of the olefin mixtureat this time.

In order to better analyze the complex product mixture, it washydrogenated to a mixture of alkanes as follows. Under nitrogen, theremaining reaction mixture from above, 4 mL of methanol, and 0.5 g 0.5%Pd/C were loaded into a 10 mL Hastelloy™ C shaker tube. The tube waspressurized with 100 psi hydrogen gas (1 psi=6.89×10³ Pascal), andheated at 85° C. for 18 h. The product mixture was analyzed using a gaschromatograph equipped with a flame ionization detector. Linear alkanes(confirmed by mass spectroscopy) containing between 7 and 28 carbonatoms could be detected. Their relative weight percent is indicated byFIG. 1.

EXAMPLE 2

This example demonstrates metathesis/isomerization of 1-dodecene. Undernitrogen, silver trifluoroacetate (37 mg, 0.17 mmol) and 1-dodecene (118mg, 0.700 mmol), were dissolved in 1 mL of toluene. To this was added[Ir(COE)₂ Cl]₂ (25 mg, 0.028 mmol). The resulting heterogeneous, brightorange reaction mixture was stirred at room temperature for 16 h, andthen analyzed by GC. Olefins containing between 4 and 26 carbon atomscould be detected; dodecene isomers accounted for approximately 15% ofthe olefin mixture.

EXAMPLE 3

This example demonstrates metathesis/isomerization of 1-octene. Undernitrogen, silver trifluoroacetate (25 mg, 0.112 mmol) and 1-octene (78mg, 0.700 mmol) were dissolved in 1 mL of toluene. To this was added[Ir(COE)₂ Cl]₂ (25 mg, 0.028 mmol). The resulting heterogeneous, brightorange reaction mixture was stirred at room temperature for 14 h, andthen analyzed by GC. Olefins containing between 4 and 22 carbon atomscould be detected; octene isomers accounted for approximately 10% of theolefin mixture.

EXAMPLE 4

This example demonstrates metathesis/isomerization of 1-octadecene.Under nitrogen, silver trifluoroacetate (49 mg, 0.224 mmol) and1-octadecene (353 mg, 1.40 mmol) were dissolved in 2 mL of toluene. Tothis was added [Ir(COE)₂ Cl]₂ (50 mg, 0.056 mmol). The resultingheterogeneous, bright orange reaction mixture was stirred at roomtemperature for 8.5 h, and then analyzed by GC. Olefins containingbetween 4 and 32 carbon atoms could be detected; octadecene isomersaccounted for approximately 10% of the olefin mixture.

EXAMPLE 5

This example demonstrates the metathesis/isomerization reaction of1-hexadecene, using silver pentafluoropropionate in place of silvertrifluoroacetate (cf. example 1). Under nitrogen, silverpentafluoropropionate (45 mg, 0.17 mmol) and 1-hexadecene (156 mg, 0.698mmol) were dissolved in 1 mL of toluene. To this solution was added[Ir(COE)₂ Cl]₂ (25 mg, 0.028 mmol). The resulting heterogeneous, brightorange reaction mixture was stirred at room temperature for 17 h, atwhich time it was analyzed by GC. Olefins containing between 4 and 28carbon atoms could be detected; hexadecene isomers accounted forapproximately 40% of the olefin mixture.

EXAMPLE 6

This example demonstrates the metathesis/isomerization reaction of1-hexadecene, using silver heptafluorobutyrate in place of silvertrifluoroacetate (cf. example 1). Under nitrogen, silverheptafluorobutyrate (54 mg, 0.17 mmol) and 1-hexadecene (125 mg, 0.557mmol) were dissolved in 1 mL of toluene. To this solution was added[Ir(COE)₂ Cl]₂ (25 mg, 0.028 mmol). The reaction mixture was stirred atroom temperature for 4 days, and then analyzed by GC. Olefins containingbetween 4 and 28 carbon atoms could be detected; hexadecene isomersaccounted for approximately 25% of the olefin mixture.

EXAMPLE 7

This example demonstrates the metathesis/isomerization reaction ofmethyl oleate to give unfunctionalized olefins, unsaturated monoesters,and unsaturated diesters over a wide range of molecular weights,followed by hydrogenation of the product mixture to give alkanes,saturated monoesters, and saturated diesters.

Under nitrogen, silver trifluoroacetate (50 mg, 0.23 mmol) and methyloleate (326 mg, 1.10 mmol) were dissolved in 3.0 mL of toluene. To thissolution was added [Ir(COE)₂ Cl]₂ (40 mg, 0. 045 mmol). The resultingheterogeneous, orange reaction mixture was stirred at 85° C. for 22 h,during which time it became red-brown. An aliquot was then taken fromthe reaction mixture and analyzed by GC: a complex mixture ofunfunctionalized linear olefins, unsaturated linear monoesters, andunsaturated linear diesters over a wide range of molecular weights waspresent; methyl oleate and its isomers accounted for approximately 50%of the reaction mixture.

In order to better analyze the complex product mixture, it washydrogenated to a mixture of alkanes, saturated monoesters, andsaturated diesters as follows. Under nitrogen, the remaining reactionmixture from above, 4 mL of methanol, and 0.5 g 0.5% Pd/C were loadedinto a 10 mL Hastelloy™ C shaker tube. The tube was pressurized with 100psi hydrogen gas, and heated at 85° C. for 18 h.

By analysis of the reaction mixture by GC/mass spectroscopy, linearalkanes containing between 9 and 26 carbon atoms, saturated linearmethyl esters containing between 8 and 28 carbon atoms, and saturatedlinear dimethyl esters containing between 11 and 26 carbon atoms couldbe detected.

EXAMPLE 8

This example demonstrates the selective metathesis of methyl oleate togive 9-octadecene and MeO₂ C(CH₂)₇ CH═CH(CH₂)₇ CO₂ Me. Under nitrogen,[Ir(COE)₂ Cl]₂ (25 mg, 0. 028 mmol) and silver trifluoroacetate (37 mg,0.167 mmol) were dissolved in 2.0 mL of toluene. The resultingheterogeneous, bright orange reaction mixture was stirred at roomtemperature for 45 h; during this time the reaction mixture becamered-brown and a grey solid precipitated. Methyl oleate (83 mg, 0.28mmol) was then added to the reaction mixture, which was stirred at roomtemperature for an additional 8 h. Analysis of the reaction mixture byGC indicated formation of the two metathesis products shown in theequation below as the major products. The molar ratio of unreactedmethyl oleate to CH₃ (CH₂)₇ CH═CH(CH₂)₇ CH₃ plus MeO₂ C(CH₂)₇CH═CH(CH₂)₇ CO₂ Me was approximately 4 to 1. ##STR5##

EXAMPLE 9

This example demonstrates the use of {Ir(COE)P(C₆ F₅)₃ Cl}₂ /AgO₂ CCF₃as a catalyst for 1-hexadecene metathesis/isomerization. Silvertrifluoroacetate (100 mg, 0.45 mmol) and 1-hexadecene (492 mg, 2.19mmol) were dissolved in 4.0 mL of toluene. To this was added{Ir(COE)P(C₆ F₅)₃ Cl}₂ (152 mg, 0.087 mmol). The resultingheterogeneous, orange reaction mixture was stirred at room temperature.An aliquot was withdrawn after 23 h, and analyzed by gas chromatography(GC): olefins containing between 4 and 28 carbon atoms each could bedetected; hexadecene isomers accounted for approximately 10% of theolefin mixture at this time.

EXAMPLE 10

This example demonstrates the use of methylene chloride as a solvent inthe metathesis/isomerization reaction of 1-octadecene (cf. example 4).Under nitrogen, silver trifluoroacetate (49 mg, 0.224 mmol) and1-octadecene (353 mg, 1.40 mmol) were dissolved in 2 mL of methylenechloride. To this was added [Ir(COE)₂ Cl]₂ (50 mg, 0. 056 mmol). Theresulting heterogeneous, bright orange reaction mixture was stirred atroom temperature for 8 h, and then analyzed by GC. Olefins containingbetween 4 and 32 carbon atoms could be detected; octadecene isomersaccounted for approximately 30% of the olefin mixture.

COMPARATIVE EXAMPLE 11

In this example, [Ir(COE)₂ Cl]₂ /AgO₂ CCF₃ is used as a catalyst for1-hexadecene metathesis/isomerization, and the molar ratio of AgO₂ CCF₃to [Ir(COE)₂ Cl]₂ is ₂ to 1. Under nitrogen, silver trifluoroacetate (12mg, 0.056 mmol) and 1-hexadecene (157 mg, 0.700 mmol) were dissolved in1 mL of toluene. To this solution was added [Ir(COE)₂ Cl]₂ (25 mg, 0.028 mmol). The resulting red-purple solution was stirred at roomtemperature for 15 h, during which time it became a heterogeneousred-brown mixture. Analysis of the reaction mixture by GC showedextensive double bond isomerization, but only trace amounts ofmetathesis products; unreacted 1-hexadecene and its isomers comprisedapproximately 90% of the olefin mixture.

COMPARATIVE EXAMPLE 12

In this example, [Ir(COE)₂ Cl]₂ /AgO₂ CCF₃ /CF₃ CO₂ H is used as acatalyst for 1-hexadecene metathesis/isomerization, and the molar ratioof AgO₂ CCF₃ to [Ir(COE)₂ Cl]₂ is 2 to 1. This example was runidentically to Comparative Example 11, except trifluoroacetic acid (16mg, 0.14 mmol) was added to the reaction mixture. Analysis of thereaction mixture by GC showed only trace amounts ofmetathesis/isomerization products; unreacted 1-hexadecene and itsisomers comprised approximately 90% of the olefin mixture.

What is claimed is:
 1. A catalyst composition comprising compounds ofFormula II and III ##STR6## wherein the molar ratio of compound III tocompound II is at least 3 to 1; and wherein X is Cl, Br, or I; R is a C₁to C₁₀ fluorinated hydrocarbyl; COE is cyclooctene; and L is cycloocteneor P(C₆ F₅)₃.
 2. The composition of claim 1, wherein X is Cl, L is COEand R is CF₃.
 3. The composition of claim 2, wherein the molar ratio ofcompound III to compound II is at least 4 to 1.